The complex dielectric constant of the material constituting a printed board, and the frequency dependency of this dielectric constant are related to the attenuation and delay of signals that are propagated through transmission paths formed inside the printed board, and are also used in the circuit simulation required in the design of high-speed transmission paths. Accordingly, the high-precision measurement of the complex dielectric of materials constituting printed boards is extremely important for increasing the precision of circuit simulations during design, and for improving the design precision.
Conventionally, for example, the complex dielectric constants of materials constituting printed boards, and the frequency characteristics of these dielectric constants, have been determined by forming a strip line resonator by sandwiching a strip conductor between layered plates comprising the material that is to be measured such as a dielectric material or the like, which forms the insulating layer of the printed board (for example, see patent document 1 or patent document 2), and obtaining the Q value of the resonance by measuring the frequency characteristics of the S parameter. Alternatively, there is also a method in which the material that is to be measured is cut out, mounted in a special tool, and measured (for example, see patent documents 3 through 8).
Moreover, a method has also been proposed in which a high-frequency circuit structure that can be used to measure the complex dielectric constant inside a printed board is constructed (for example, see patent documents 9 through 13). FIG. 9 is a schematic sectional view showing the construction of the high-frequency circuit described in patent document 10. In the high-frequency circuit 100 described in patent document 10, as is shown in FIG. 9, a plurality of conductor layers is stacked via insulating layers, and a circuit pattern 121 in which various types of parts are attached is formed on the surface.
Furthermore, an internal electrode 122 containing passive circuits such as a matching line, choke line, and the like is formed beneath the circuit pattern 121 via an insulating layer 111, and the ground electrode 123 of the strip-line resonator constituting a high-frequency circuit is formed beneath this via an insulating layer 112. Furthermore, a central conductor 124 of the strip-line resonator is formed beneath the ground electrode 123 via an insulating layer 113, and the ground electrode 125 of the strip-line resonator is formed beneath this via an insulating layer 114. Furthermore, an insulating layer 115 is formed as the lowermost layer, and a side-surface electrode 126 is formed so as to cover the side surface of this layered assembly. Moreover, through-holes are formed in the internal parts of the respective insulating layers, and conductor layers are formed on the inside surfaces of these through-holes, so that the circuit pattern 121 and central conductor 124 are appropriately connected.
In this high-frequency circuit 100, the pattern of the ground electrode 123 is formed with a shape which is such that no electrode is formed in the area corresponding to the shape of the central conductor 124, thus lowering the capacitance between the ground electrode 123 and central conductor 124, and improving the Q value of the strip-line resonator.    Patent Document 1: Japanese Laid-Open Utility Model Application No. 6-74974    Patent Document 2: Japanese Laid-Open Utility Model Application No. 6-77312    Patent Document 3: Japanese Laid-Open Patent Application No. 6-331670    Patent Document 4: Japanese Patent Publication No. 8-20481    Patent Document 5: Japanese Laid-Open Patent Application No. 7-140186    Patent Document 6: Japanese Laid-Open Patent Application No. 8-220160    Patent Document 7: Japanese Laid-Open Patent Application No. 2003-331220    Patent Document 8: Japanese Laid-Open Patent Application No. 2004-45262    Patent Document 9: Japanese Laid-Open Patent Application No. 10-51235    Patent Document 10: Japanese Laid-Open Patent Application No. 10-51236    Patent Document 11: Japanese Laid-Open Patent Application No. 2000-183233    Patent Document 12: Japanese Laid-Open Patent Application No. 2003-168761    Patent Document 13: Japanese Laid-Open Patent Application No. 2003-309403